The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.
During transmission of a video stream over a lossy transmission channel, data corresponding to one or more regions of the video stream may be lost. When such a video with lost data is decoded by a decoder at the receiver, the rendered video content may be riddled with one or more artifacts such as blocking artifacts, corrupted content, and the like. For example, when multiple regions of data are lost while transmission, the rendered video may comprise gray regions that correspond to the lost regions. In scenarios, when multiple regions are combined to form a slice before transmitting, a loss of data corresponding to the transmitted slice may result in blanking of an entire region corresponding to the slice in the rendered signal. In certain other scenarios, the aforementioned artifacts may be introduced in the rendered video due to block-based encoding applied to compress the data corresponding to the video stream at the encoder. As the applied block-based encoding may correspond to a lossy compression technique, the transmitted data corresponding to the video stream may not be reproducible leading to artifacts in the rendered video content. To avoid such artifacts in the decoded signal, one of the mostly adopted error concealment techniques by the decoders is to replace the lost region with the corresponding region from a previously decoded frame. Such a replacement makes use of the inherent property of redundancy of the transmitted video stream.
In accordance with the existing techniques of error concealment, one or more parameters associated with filters at the decoder may be controlled for recovery of lost regions. Other techniques of error concealment comprise division of a region around a lost ration into a plurality of regions to calculate edge orientation of each of the plurality of regions. The data corresponding to the lost region may be retrieved based on directional interpolation in the direction of the calculated edge orientations. In accordance with other error concealment technique, the header of the received frames may be analysed to determine the presence of the lost regions. Based on the analysis, the error regions may be isolated to improve the quality of the received content. Other error concealment techniques make use of an adaptive mix of Forward Error Correction (FEC) and/or Automatic Repeat Request (ARQ) to reduce the errors in the received content.
However, when the video comprises significant motion in the constituting frames, the aforementioned error concealment techniques may not be effective. For example, in case of significant motion variation associated with the frames of the video stream, the decoded video after error concealment may comprise frozen regions that may not be spatially related to adjacent regions. Similarly, the aforementioned error concealment technique may not yield satisfactory results when the frames constituting the video stream are temporally related. Hence, in order to pre-empt the occurrence of an artifact in the rendered video content and to enhance the quality of the rendered video content, it may be desirable to detect artifacts even after error concealment has been performed by the decoder.